#include<bits/stdc++.h>
using namespace std;
double x;//三次方
const double eps = 1e-7;//要求精度为6位小数,精度就设为7
bool check(double mid){
    if (mid*mid*mid>x)
        //太大
        return true;
    
    else return false;
}
double f_bin_search(double l,double r){
    double mid = (l+r)/2;
    
    while(r-l>eps){
	    mid = (l+r)/2;
        if (check(mid)){
            r = mid;
        }else l = mid;
    }
    return l;
}
int main(){
    cin>>x; //-10000 ~10000
    double res = f_bin_search(-10000.01,10000.01);
    printf("%.6f",res);
    return 0;
}
